1. Field of the Invention
The present invention broadly relates to an electromechanical shutter device for blocking and passing a light beam with a movable shutter member by using electromagnetic, instead of mechanical, forces. The present invention also broadly relates to a system which uses a shutter state machine to electronically control the movement of the shutter member between positions for blocking or passing the light beam. The present invention further broadly relates to a method for electronically controlling the movement of the shutter member to block or pass the light beam.
2. Related Art
Developers of information storage devices and methods continue to seek increased storage capacity. As part of this development, holographic memory systems have been suggested as alternatives to conventional memory devices. Holographic memory systems may be designed to record data as one bit of information (i.e., bit-wise data storage). See McLeod et al. “Micro-Holographic Multi-Layer Optical Disk Data Storage,” International Symposium on Optical Memory and Optical Data Storage (July 2005). Holographic memory systems may also be designed to record an array of data that may be a 1-dimensional linear array (i.e., a 1×N array, where N is the number linear data bits), or a 2-dimensional array commonly referred to as a “page-wise” memory system. Page-wise memory systems may involve the storage and readout of an entire two-dimensional representation, e.g., a page of data. Typically, recording light passes through a two-dimensional array of low and high transparency areas representing data, and the system stores, in three dimensions, the pages of data holographically as patterns of varying refractive index imprinted into a storage medium. See Psaltis et al., “Holographic Memories,” Scientific American, November 1995, where holographic systems are discussed generally, including page-wise memory systems.
Holographic data storage systems may perform a data write (also referred to as a data record or data store operation, simply “write” operation herein) by combining two coherent light beams, such as laser beams, at a particular point within the storage medium. Specifically, a data-encoded light beam may be combined with a reference light beam to create an interference pattern in the holographic storage medium. The pattern created by the interference of the data beam and the reference beam forms a hologram which may then be recorded in the holographic medium. If the data-bearing beam is encoded by passing the data beam through, for example, a spatial light modulator (SLM), the hologram(s) may be recorded in the holographic medium.
Holographically-stored data may then be retrieved from the holographic data storage system by performing a read (or reconstruction) of the stored data. The read operation may be performed by projecting a reconstruction or probe beam into the storage medium at the same angle, wavelength, phase, position, etc., as the reference beam used to record the data, or compensated equivalents thereof The hologram and the reference beam interact to reconstruct the data beam.
To mechanically block or switch a beam, the shutter which blocks/switches the beam needs to be moved across the beam diameter. This shutter needs to accelerate, traverse the beam, and then decelerate to a stop on the opposite side of the beam. To minimize the movement time, the acceleration needs to be maximized. This means a high force may need to be applied to a low mass. This provides a high acceleration and low power consumption if the actuation can be accomplished with a highly efficient actuator design. Present designs block the entire beam, using, for example, heavy metal shutters and inefficient motor designs. See, for example, U.S. Pat. No. 3,664,251 (Vicent), issued May 23, 1972; U.S. Pat. No. 5,502,524 (Bovenzi et al.), issued Mar. 26, 1996; and U.S. Pat. No. 5,517,267 (Tanabe), issued May 14, 1996. This leads to slower times and higher power consumption, which limits the performance and lifetime of these shutters.